Tank smells powerfully of rotten eggs

[asylumdown]

This appears to have starts this morning, to the point where the whole house smells like sulphur. I am at a loss to explain this, corals are all happy, fish are fine, snails and crabs are motoring about. The only thing that's died recently was an elegance coral, but it's skeleton has been free of tissue for several days. I was having an issue with my r/o water smelling a bit off, so I cleaned the unit and replaced all the cartridges, and now the R/O system is working perfectly. I also siphoned about 5 gallons of water out of the tank and took it to another room to be sure it's the water, and it's definitely emitting a potent rotten egg smell. I am getting a little worried...

Any ideas? Even a dead snail couldn't make 375 gallons of water smell this bad.

[Proteus]

Hydrogen sulfide (h2s)

If you disturbed sand at all it will realese. You can dose peroxide to oxidize it. Ussually I think it's 1ml per gallon. But I would cut that in half to start

[martinmcnally]

This can also happen if you are running bio pellets and they have become stagnated.

[asylumdown]

I'm running bio pellets, it's a recirculating reactor so the pellets tumble regardless of how much flow through there is, but it's possible that the outlet got clogged so not enough water was escaping the reactor. I just cleaned all the screens on it.

I also stupidly did not think of the emergency drain that is underneath my sump. It's in the world's least convenient spot so I don't pour water down it very often. I just topped it off in case the drain trap dried out and it was sewer gas that was escaping in to my cabinet, but that shouldn't have made the water itself smell should it?

[Rogue951]

run lots of carbon help rid the smell....
If nothing died I'm leaning towards the disturbed sand bed or pellet reactor explanation.

[Myka]

You can leave a bowl of carbon near the tank to help with the smell in the air too, plus a new refill in the tank wouldn't hurt.

Why did you leave the Elegance skeleton in the tank long enough for the tissue to all fall off? That's a lot of nutrient waste.

Try collecting some water from the outlet of the biopellet reactor. If that is the source that water should smell very strong.

[tentacles]

I don't think carbon will adsorb H2S under normal conditions; Wikipedia mentions using carbon as a substrate coated with a catalyst for reacting the H2S into less toxic/smelly compounds.

I think your best bet is probably some light peroxide dosing. And maybe check that biopellet reactor for cleanliness, if it's clogged and that smell is the bacteria dying off...

[Myka]

If there is a high oxygen level in the sump (such as after the skimmer) then the H2S will be at least partially oxidized where it can be removed by carbon. If there is H2S smell in the air carbon will remove it. GFO will also remove H2S.

[Myka]

There is this too... old, but still good info. http://reefkeeping.com/issues/2005-12/rhf/index.php

It mentions carbon and GFO, and gives you some steps to resolution.

[Dearth]

I deal with H2S a lot at my work although in considerably larger quantities than an aquarium tank will release and one of the easier ways to get rid of or diffuse the H2S is to have a continuous airflow with fresh air. All is required is a standard house fan and a source of fresh air IE. another room, fresh air from outside or just circulate throughout house. You can smell as little as 2 parts per million of H2S and while not generally harmful at those lvls prolonged exposure will give you symptoms but over a period of days anything over 10 parts is considered to be detrimental in as little as 8 hrs.

However that being said if you feel nauseous or have a headache from the H2S smell stop circulating the air immediately and go outside for fresh air and drink plenty of water till you no longer feel nauseous or headache has gone fresh air is the best and easiest way to diffuse H2S I don't think aquarium tanks will produce enough h2s to cause those issues but you never know.